1. Field of the Invention
The invention relates generally to stoves and furnaces, and specifically to solar heat storage. A heat storage reservoir for use in solar heating apparatus or heat pumps is disclosed.
2. Description of the Prior Art
Solar heat collection is well known and may be accomplished by a wide variety of solar collectors that circulate hot air, hot water, and like fluids. Once the collector has heated the fluid, a long standing problem has been to adequately store the heat for later extraction and use. One of the oldest known storage techniques is to direct the heat energy or the heated fluid into a container of stones within an insulated room, as taught in U.S. Pat. No. 608,755 to Cottle. Similar teaching appears in U.S. Pat. No. 965,391 to Little, and U.S. Pat. No. 3,369,541 to Thomason. Stones, rocks, concrete blocks, bricks, and the like are well suited to receive heat over a prolonged period, such as the daylight hours of the day when sunlight can be converted to heat, and then radiate the heat for a further prolonged period, such as the night hours of the day.
In addition to stones, liquids are known as a heat storage media. In the above mentioned patent to Thomason, a central water tank is the primary heat exchanger for a heating system, and a surrounding bed of stones may exchange heat with the water tank. In other art such as U.S. Pat. No. 2,388,940 to Taylor and U.S. Pat. No. 3,029,806 to Okuda, special tanks and bag-like containers are used to store solar heated water. Liquids often have higher specific heat than rocks, and water conducts heat more rapidly than rocks, but solid heat storage media is often more feasible. Note: Water conducts heat much faster than stones. For example, water cannot effectively store heat at a temperature above boiling. Often a water storage system requires a heat exchanger in the liquid to bring air to a directly useable temperature for heating purposes. A rock bed provides heat storage and air-heating capability without an added heat exchanger.
Rock bed storage has a number of problems, one of the most serious being that air flow through a rock bed is not predictable because of the random shapes of the rocks. If air flow is too restricted through a rock bed, it is necessary to remove and reinstall the rock pile with air channels. Further drawbacks of rock storage include the labor and expense of moving rock piles and washing rock piles. Even after a rock bed storage system is properly in place, the rocks remain a source of dirt and dust and are capable of growing bacteria and fungus. While the life of a rock bed is quite long, certain types of rock bed have been reported to break up occasionally.
The invention maintains the many advantages inherent in rock bed heat storage media and overcomes all of the problems listed above. Further advantages will be evident from the description below.